0-9 | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
An active element in the n-th layer of the Open Systems Interconnection--Reference Model (OSI-RM) that (a) interacts directly with elements, i.e. , entities, of the layer immediately above or below the n-th layer, (b) is defined by a unique set of rules, i.e. , syntax, and information formats, including data and control formats, and (c) performs a defined set of functions. Note 1: The n refers to any one of the 7 layers of the OSI-RM. Note 2: In an existing layered open system, the n may refer to any given layer in the system. Note 3: Layers are conventionally numbered from the lowest, i.e., the physical layer, to the highest, so that the n + 1 layer is above the n-th layer and the n- 1 layer is below.